In addition to Hard Disk Drives (HDD), Solid State Drives (SSD) are also used as an external storage device for personal computers and other information processing devices. SSDs typically include a nonvolatile semiconductor memory, such as a Negated AND or NOT AND (NAND) type flash memory.
A management table is needed to uniquely associate the user data input from a host with the address of the physical storage region of the NAND-type flash memory for SSD. It is necessary to write the management table along with the user data stored in a data buffer inside the SSD into the NAND-type flash memory until the power of the external power supply stops.
However, since it is necessary to write all of the user data and the management table into the NAND-type flash memory, a storage battery with high capacity is needed as a backup power supply. Also, the management table usually has a data size that is about 1/1000 of the storage capacity of the SSD. However, the data size of the management table increases along with an increase in the storage capacity of the SSD. Therefore, it is necessary to increase the capacity of the storage battery to account for these increases. However, it is difficult to assemble a storage battery with high capacity due to the size restrictions of the packaging of the SSD.